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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

GLACIERS NEAR THE COPPER RIVER DELTA                   893
forest at the very edge of the glacier proves that the glacier has not been notably larger for a much greater period.
McPherson Glacier. McPherson Glacier1 is a moderate-sized ice tongue on the eastern side of Copper River south of Miles Glacier. The main ice tongue has a length of over 4 miles, and a width at the terminus of about a quarter of a mile. It is fed by two tributaries from the southeast, each about 8 miles in length, the northernmost heading on a 6(200 foot divide from which a tributary also flows northward to the Miles Glacier. This ice tongue is not known to have oscillated significantly in recent years. It was retreating when visited by the junior author in 1910.
'" In its lower portion McPherson Glacier emerges from a hanging valley, and the terminus of the glacier cascades 800 to 1000 feet over the lip of this hanging valley, ending at the base of a steep rock slope at an elevation of 310 feet above sea level. It is a conspicuous object from the railway, because of the clean, crevassed condition of this terminal cascade. That the cascading portion of the glacier is thin, is proved by the emergence of a rock ledge about half way up the slope; and it is as little crevassed as a glacier could be on so steep a slope. This terminal ice cascade occupies only the southern hah* of the lip of the hanging valley, and that it has recently diminished several hundred feet is proved by a barren zone on the northern side. For many years the ice has not covered the remainder of the northern half of the valley lip, for there are dense thickets of willow and alder and scattered spruce trees upon it. There is no further evidence as to recent changes in this glacier.
At a distance of about 100 yards in front of McPherson Glacier, striated, rounded rock ledges constrict the valley, and a short distance farther west another rock ledge from the north projects part way across the valley. On approaching McPherson Glacier from the railway, these ledges give one the impression that they are large terminal moraines, but although morainic material has accumulated on them, there are no independent moraines here, though there is a low terminal moraine nearer the glacier.
Sheep Creek, the stream from McPherson Glacier, has built an extensive outwash gravel plain, above the level of which are^forested terraces of older outwash. The plain broadens westward and coalesces with the great outwash gravel plain of the Copper River.
GLACISES EAST OF COPPER RIVEB DELTA
Johnson Glacier. Johnson Glaciers (PI. XCIII), south of McPherson Glacier, is fed by four long narrow tributaries, the main ice stream having a length of 5^ miles, and a width of about hah* a mile near the terminus which is less than 200 feet above sea level. It is over 8 miles from the end of the main glacier to the head of the longest of the tributaries. All these tributaries rise in snowfields 4000 to 5000 feet above sea level, the longest one on the north heading on a divide which also sends a tributary northward to Miles Glacier. Each of the tributaries cascades steeply down the mountain slopes.
i Named in 1910 for J. L. McPherson of Seattle who made a railway survey up the Copper River valley during the winter of 1006.
i Named in 1910 for Albert 0. Johnson, one of the bridge engineers of the Copper Hiver and Northwestern Railway, who made many instrumental observations upon the glaciers and glacial streams between 1908 and 1910.